1. Field of the Invention
This invention relates to a die for bending and machining a metallic plate, and more particularly a bending die having a rotary die.
2. Description of the Prior Art
As this kind of prior art bending die, there is provided an invention described in the gazette of U.S. Pat. No. 5,341,669, for example. This prior art product is formed to have a rotary bending head, a saddle block having a bearing surface and a retaining key for holding the aforesaid head and a member for returning the aforesaid head or the like.
The aforesaid prior art product is constructed such that the rotary bending head is rotated while it is slidably contacted with the bearing surface of the saddle block. Accordingly, in the case of the prior art product, the outer circumferential surface or the bearing surface of the rotary bending head had to be machined in a quite high accuracy. Because if these locations show a poor machining accuracy, the rotary bending head is not rotated smoothly, resulting in that this may cause a trouble in operation.
As a result, the prior art product had a problem that it took much time to machine the outer circumferential surface of the rotary bending head or the bearing surface of the saddle block and needed a high machining cost.
In addition, as shown in FIGS. 5 and 6, it is desirable that this kind of bending die is formed such that a contact point K (hereinafter called as a dividing point) between the upper edge 1b of the lower die 1 and the outer edge 5a of the formed part 5 formed at the rotary die 3 can be properly selected at the most suitable location in response to a product design.
Because if this dividing point may not be freely changed, it sometimes occurs that the products such as a fender or a pillar in an automobile having a curved surface or a bulged-out portion, for example, can not be pressed in a neat manner strictly in accordance with designs of the curved surface or bulged-out portion.
However, the prior art product was constructed such that the rotary bending head is directly supported by the saddle block. Accordingly, in the case of the prior art product, since the rotary bending head was formed into a column-like shape, if the dividing point was selected to exceed the diameter of the dividing point, the rotary bending head could not be rotated smoothly and the dividing point had to be selected usually at the position of the same distance from the center of the head over a longitudinal direction of the rotary bending head. As a result, in the case of this kind of prior art bending die, it showed a problem that the products having a curved surface or a bulged-out portion such as a fender or a pillar in an automobile could not be pressed in an accurate manner strictly in accordance with their design.